This invention relates to a bending device for use, for example, in an endoscope.
As is well known, an endoscope comprises a hollow body, a flexible insertion portion extending from a front end of the body, a flexible bending portion extending from a distal end, of the insertion portion, and a rigid portion provided at a distal end of the bending portion. An inspection window and an illumination window are formed at the rigid portion.
Japanese Utility Model Publication No. 9274/77 discloses a flexible tube structure for an endoscope which structure has one coil and a resilient thin plate. FIG. 1 of Japanese Laid-Open (Kokai) Utility Model Application No. 10605/80 shows an example in which this flexible tube structure is applied to a bending portion of an endoscope. More specifically, in the bending portion, the resilient thin plate is received in an internal space defined by the coil and extends in the longitudinal direction of the coil. Recesses are formed in each of opposite lateral edges of the resilient thin plate, and are juxtaposed in the longitudinal direction of this plate. The turn portions of the coil are engaged in the recesses. The bending portion is bent in a direction perpendicular to the plane of the resilient thin plate by an operating wire, so as to direct an inspection window and an illumination window of the rigid portion toward a desired direction.
The above resilient thin plate performs two functions. The first function is to prevent the coil from being axially compressed when pulling the operating wire, thereby ensuring a proper bending of the bending portion. The second function is to limit the direction of bending of the bending portion to a direction perpendicular to the plane of the resilient thin plate.
The above bending portion is simple in construction, and can be easily manufactured. However, since the resilient thin plate is received in the internal space of the coil in such a manner that this plate divides the internal space into two space portions, the resilient thin plate is obstructive when optical fiber bundles, guide tubes and etc., are to be inserted into the internal space. As a result, considerable limitations are imposed on the thicknesses or diameters of the optical fiber bundles and the guide tubes. Moreover, a dead space tends to be present in the two space portions, thus failing to make effective use of the internal space.
Referring to another prior art, Japanese Laid-Open Utility Model Application No. 110443/77 discloses a fiber scope including a bellows which is not designed to be bent by an operating wire.